Effect of median-nerve electrical stimulation on BOLD activity in acute ischemic stroke patients

ObjectiveTo investigate blood oxygenation level-dependent (BOLD) activation during somatosensory electrical stimulation of the median nerve in acute stroke patients and to determine its correlation with ischemic damage and clinical recovery over time.MethodsFourteen acute stroke patients underwent functional magnetic resonance imaging (fMRI) during contralesional median-nerve electrical stimulation 12–48 h after stroke. Findings were then validated by diffusion tensor imaging (DTI) and motor evoked potential by transcranial magnetic stimulation (TMS).ResultsPoor clinical recovery at three months was noted in four patients with no activation in the early days after stroke, whereas good clinical recovery was observed in eight patients with a normal activation pattern in the primary sensory motor area in the acute phase. In two patients BOLD activation correlated weakly with clinical recovery. Findings from TMS and DTI partially correlated with clinical recovery and functional scores.ConclusionsClinically relevant insights into the “functional reserve” of stroke patients gained with peripheral nerve stimulation during fMRI may carry prognostic value already in the acute period of a cerebrovascular accident.SignificanceBOLD activation maps could provide insights into the functional organization of the residual systems and could contribute to medical decision making in neurological and rehabilitative treatment.

► The study investigates the predictive value of a passive task in 3T fMRI in the early phase of stroke.
► The absence of BOLD activation during sensory stimulation in the acute phase is associated with poorer clinical recovery.
► The presence of BOLD activation in the early hours after stroke seems to be related to better clinical recovery.
► A subject-specific HRF for acute stroke patients provides reliable BOLD activation maps.